Light down conversion film and display backlight unit using the same

Abstract

The disclosure provides a display backlight unit and its light down conversion film. The light down conversion film may include a quantum-dot layer sandwiched between input substrate and an exit substrate. First and second refractive asymmetric micro-prisms are disposed on two opposite input and first exit surfaces of the input substrate, respectively. On the input surface of the input substrate, multiple arrays of the asymmetric refractive asymmetric micro-prisms preserve the large off-axis angle of incident light with first wavelength. On the first exit surface of the input substrate, multiple arrays of the refractive asymmetric micro-prisms increase the reflectance of the large incident angle light. A second exit surface of the exit substrate includes refractive symmetric micro-prisms. The refractive asymmetric micro-prisms of the input substrate and the refractive asymmetric micro-prisms of the exit substrate have rounded tips and valleys for enhancing refraction of the first light and the second light.

What is claimed is: 
     
       1. A display backlight unit, comprising:
 at least one light source comprising a light emission window and adapted to emit first light with first wavelength through the light emission window; 
 a light guide plate located adjacent to the light emission window of the at least one light source, the light guide plate including an input edge and a light-guide exit surface and adapted to receive the first light via the input edge and spread out the first light within the light guide plate, then extract the first light uniformly over the back light unit, the first light extracted exiting the light guide plate via the light-guide exit surface at a range of off-axis angles, and an illuminance of the first light extracted being allowed to have fluctuations across the back light unit; and 
 a light down conversion film comprising at least one quantum-dot layer with more than one population of quantum dots and at least one input substrate, the input substrate disposed on the light-guide exit surface of the light guide plate, the quantum dots adapted to absorb a part of the first light with first wavelength which exits the light guide plate and the input substrate in sequence before down-converting into second light with second wavelength and reemitting, another part of the first light which is unabsorbed passing through the light down conversion film, and the first wavelength being shorter than the second wavelength; 
 wherein the input substrate includes an input surface facing towards the light guide plate and a first exit surface facing towards the quantum-dot layer, the input surface comprises a plurality of first refractive asymmetric micro-prisms, wherein each of the first refractive asymmetric micro-prisms includes a first steep segment facing toward the input edge of the light guide plate and a first shallow segment connected to the first steep segment, the first exit surface of the input substrate is facing the quantum-dot layer, the first exit surface of the input substrate comprises a plurality of second refractive asymmetric micro-prisms and each includes a second steep segment facing away from the input edge of the light guide plate and a second shallow segment connected to the second steep segment, the first steep segments and the first shallow segments adjacent to each other form a first rounded tip and a first rounded valley for refraction of the first light and the second light, and the second steep segments and the second shallow segments adjacent to each other form a second rounded tip and a second rounded valley for refraction of the first light and the second light. 
 
     
     
       2. The display back light unit of  claim 1 , wherein the first refractive asymmetric micro-prisms and the second refractive asymmetric micro-prisms are parallel to the input edge of the light guide plate, each of the first refractive asymmetric micro-prisms and the second refractive asymmetric micro-prisms on the input substrate has a base width between 10 um to 200 um, each of the first rounded tips of the first refractive asymmetric micro-prisms and the second rounded tips of the second refractive asymmetric micro-prisms has a radius smaller than 10 um, each of the first rounded valleys between the first refractive asymmetric micro-prisms and the second rounded valleys between the second refractive asymmetric micro-prisms has a radius smaller than 10 um. 
     
     
       3. The display back light unit of  claim 1 , wherein both of a surface of the first refractive asymmetric micro-prisms including the first rounded tips and a surface of the first refractive asymmetric micro-prisms including the rounded tips have random areas of plane, curving, sagging, bumping and waviness. 
     
     
       4. The display back light unit of  claim 1 , wherein each of the first refractive asymmetric micro-prisms and second refractive asymmetric micro-prisms on the input substrate has a height between 1 um to 50 um. 
     
     
       5. The display back light unit of  claim 1 , wherein each of the first refractive asymmetric micro-prisms has a tilt angle of the first steep segments and the input surface between 50 degrees to 89 degrees, and each the second refractive asymmetric micro-prisms on the input substrate has a tilt angle of the second steep segments and the first exit surface between 50 degrees to 89 degrees. 
     
     
       6. The display back light unit of  claim 1 , wherein each of the first refractive asymmetric micro-prisms on the input substrate has a tilt angle of the first shallow segment and the input surface between 1 degree to 40 degrees, and each if the second refractive asymmetric micro-prisms on the input substrate has a tilt angle of the second shallow segment and the first exit surface between 1 degree to 40 degrees. 
     
     
       7. The display back light unit of  claim 1 , wherein the light down conversion film further comprises at least one exit substrate being away from the light guide plate and attached to a side of the quantum-dot layer opposite to the input substrate, and the quantum-dot layer is sandwiched between the input substrate and the exit substrate, wherein the part of the first light which is unabsorbed is adapted to pass through the light down conversion film and towards the exit substrate. 
     
     
       8. The display back light unit of  claim 7 , wherein the exit substrate comprises a second exit surface and a plurality of refractive symmetric micro-prisms with tips and valleys located on the second exit surface. 
     
     
       9. The display back light unit of  claim 8 , wherein the tips and valleys of the refractive symmetric micro-prisms of the exit substrate are sharp. 
     
     
       10. The display back light unit of  claim 8 , wherein cross-sections of the refractive symmetric micro-prisms are perpendicular to the input edge of the light guide plate, each of the refractive symmetric micro-prisms on the exit substrate has a base width between 10 um to 200 um, the tips of the refractive symmetric micro-prisms have radius smaller than 10 um, the valleys between the refractive symmetric micro-prisms have radius smaller than 10 um. 
     
     
       11. The display back light unit of  claim 8 , wherein each refractive symmetric micro-prism on the exit substrate has a first segment and a second segment that are connected with each other and forming an included angle between 60 degrees to 120 degrees therebetween. 
     
     
       12. The display back light unit of  claim 11 , wherein the first segment and the second segment of the refractive symmetric micro-prisms on the exit substrate have tilt angles between 30 degrees to 60 degrees. 
     
     
       13. The display back light unit of  claim 8 , wherein the refractive symmetric micro-prisms on the exit substrate have heights between 1 um to 50 um. 
     
     
       14. The display back light unit of  claim 8 , wherein a refractive index of the quantum-dot layer, a refractive index of the input substrate and a refractive index of the exit substrate are identical. 
     
     
       15. The display back light unit of  claim 8 , wherein a refractive index of the quantum-dot layer, a refractive index of the input substrate, and a refractive index of the exit substrate are different. 
     
     
       16. A light down conversion film, comprising:
 a quantum-dot layer with more than one population of quantum-dots, and an input substrate including an input surface and a first exit surface that are opposite to each other and a plurality of first refractive asymmetric micro-prisms disposed on the input surface, the input substrate for receiving first light from the input surface, the first exit surface facing towards the quantum-dot layer, the quantum dots for absorbing a part of the first light with first wavelength from the first exit surface of the input substrate then down-converting into second light with second wavelength and reemitting, another part of the first light which is unabsorbed passing through the quantum-dot layer, each of the first refractive asymmetric micro-prisms including a first steep segment facing away from the quantum-dot layer and a first shallow segment connected to the first steep segment, the first steep segments and the first shallow segments adjacent to each other forming a first rounded tip and a first rounded valley therebetween for refraction of the first light and the second light, and the first wavelength being shorter than the second wavelength. 
 
     
     
       17. The light down conversion film of  claim 16 , wherein the first exit surface of the input substrate comprises a plurality of second refractive asymmetric micro-prisms each including a second steep segment facing towards the quantum-dot layer and a second shallow segment connected to the second steep segment, wherein the second steep segments and the second shallow segments adjacent to each other form a second rounded tip and a second rounded valley therebetween for refraction of the first light and the second light. 
     
     
       18. The light down conversion film of  claim 16 , further comprising at least one exit substrate disposed on a side of the quantum-dot layer away from the input substrate, the quantum-dot layer sandwiched between the input substrate and the exit substrate, the part of the first light which is unabsorbed adapted to pass through the quantum-dot layer and towards the exit substrate, the exit substrate comprising an second exit surface located oppositely away from the quantum-dot layer and a plurality of refractive symmetric micro-prisms with tips and valleys disposed on the second exit surface. 
     
     
       19. A light down conversion film, comprising:
 at least one quantum-dot layer with more than one population of quantum-dots, and an input substrate comprising an input surface facing towards the quantum-dot layer, a first exit surface facing towards the quantum-dot layer and a plurality of refractive asymmetric micro-prisms disposed on the first exit surface, the input substrate for receiving first light from the input surface, the quantum-dots for absorbing a part of the first light with first wavelength from the first exit surface of the input substrate then down-converting into second light with second wavelength and reemitting, another part of the first light which is unabsorbed passing through the quantum-dot layer, each of the refractive asymmetric micro-prisms including a first steep segment facing towards the quantum-dot layer and a first shallow segment connected to the first steep segment, the first steep segments and the first shallow segments adjacent to each other forming a first rounded tip and a first rounded valley for refraction of the first light and the second light, and the first wavelength being shorter than the second wavelength. 
 
     
     
       20. The light down conversion film of  claim 19 , wherein the light down conversion film further comprising at least one exit substrate disposed on a side of the quantum-dot layer away from the input substrate, the quantum-dot layer sandwiched between the input substrate and the exit substrate, the part of the first light which is unabsorbed adapted to pass through the quantum-dot layer and towards the exit substrate, the exit substrate comprising a second exit surface and a plurality of refractive symmetric micro-prisms with tips and valleys disposed on the second exit surface for refraction of the first light and the second light.